China's Alibaba Group said on Wednesday it would invest US$1 billion into its Aliyun cloud computing arm to challenge Amazon.com lucrative Web Services division, opening a global front in the battle between the two e-commerce giants. With the global cloud computing market estimated by analysts to be worth about US$20 billion, Alibaba said in a statement the investment would go toward setting up new Aliyun data centres in the Middle East, Singapore, Japan and Europe .